Modern cooking appliances, especially stoves, may conceal the burners beneath a glass-ceramic plate which is heated by the combustion of gas below the plate so that pots or the like placed upon the glass-ceramic plate will be heated for cooking and other purposes.
For this purpose, below the glass-ceramic plate, a gas jet burner can be provided with a nozzle plate from which gas jets emerge and are burned, the burner distributing the gas to the orifices of the plate.
The apparatus generally comprises, as well, an igniter for initiating the combustion of the gas jets, a supply of the fuel gas and a magnetic valve for controlling the feed of the gas to the burner. In addition, it is customary to provide a control arrangement allowing the gas supply to be turned on and off and a monitoring device for monitoring the operation of the gas burner, for example, to shut down the gas supply should the flame be extinguished for any length of time or should the ignition fail.
Reference may be had to the commonly assigned U.S. Pat. No. 4,830,602 which describes a gas range having at least one burner covered by a glass-ceramic plate forming the cooking field. The cooking burner which is commonly used to ignite the main burner of conventional cooking units of this type is generally positioned sufficiently close to the main burner that a reliable ignition can be ensured.
For the most part, such a gas range can have a plurality of cooking fields, i.e. zones of the glass-ceramic plate at which cooking can occur and each of which can be provided with a respective burner below the glass-ceramic plate. These burners are supplied in an electrotechnical sense, in parallel. The burner may have a surface screen or display indicating the status of the burners.
In an earlier cooking apparatus or range of this type, for example, the range described in German patent document DE 26 41 274, a glow igniter is provided and is integrated in the monitoring unit so that it is constantly energized. Under these circumstances, a failure to ignite the main burner can occur only when the glow igniter itself fails to operate properly.
To monitor for failures, a special monitoring unit is provided which is associated with a safety magnetic valve shutting down the gas feed to the main burner when the current supplied to the glow igniter is detected to fail. A system of this type is comparatively expensive since it requires a special safety magnetic valve in addition to the main control valve.
For the most part, the reliability of the gas range depends largely upon the reliability of the safety magnetic valve. This cannot always be ensured.
Furthermore, since the glow igniter is constantly energized in such systems, the glow igniter operates at a higher temperature than would be the case if the glow igniter were to be intermittently energized and this continuously higher operating temperature has been found to decrease the useful life of the glow igniter. A premature failure of the glow igniter, moreover, may render the range completely or partially inoperative.
An advantage of this system, however, is that the glow igniter ensures uniform ignition without explosions or the like. By contrast, other range designs known to the art, utilizing, for example, spark ignition or high-voltage ignition, give rise to nonuniform ignition and detrimental explosions. High-voltage systems, moreover, have been found to be environmentally unsound since they create radio and television interference which cannot be readily supervised.